sd-bus: make BUS_DEFAULT_TIMEOUT configurable

This adds sd_bus_{get,set}_method_call_timeout().
If the timeout is not set or set to 0, then the timeout value is
parsed from $SYSTEMD_BUS_TIMEOUT= environment variable. If the
environment variable is not set, then built-in timeout is used.

doc/ENVIRONMENT.md

@@ -37,6 +37,11 @@ All tools:
   useful for debugging, in order to test generators and other code against
   specific kernel command lines.
 
+* `$SYSTEMD_BUS_TIMEOUT=SECS` — specifies the maximum time to wait for method call
+  completion. If no time unit is specified, assumes seconds. The usual other units
+  are understood, too (us, ms, s, min, h, d, w, month, y). If it is not set or set
+  to 0, then the built-in default is used.
+
 systemctl:
 
 * `$SYSTEMCTL_FORCE_BUS=1` — if set, do not connect to PID1's private D-Bus

src/libsystemd/libsystemd.sym

@@ -573,4 +573,6 @@ global:
 
 LIBSYSTEMD_240 {
         sd_bus_message_readv;
+        sd_bus_set_method_call_timeout;
+        sd_bus_get_method_call_timeout;
 } LIBSYSTEMD_239;

src/libsystemd/sd-bus/bus-internal.h

@@ -316,6 +316,9 @@ struct sd_bus {
 
         int *inotify_watches;
         size_t n_inotify_watches;
+
+        /* zero means use value specified by $SYSTEMD_BUS_TIMEOUT= environment variable or built-in default */
+        usec_t method_call_timeout;
 };
 
 /* For method calls we time-out at 25s, like in the D-Bus reference implementation */
@@ -333,8 +336,7 @@ struct sd_bus {
 
 #define BUS_CONTAINER_DEPTH 128
 
-/* Defined by the specification as maximum size of an array in
- * bytes */
+/* Defined by the specification as maximum size of an array in bytes */
 #define BUS_ARRAY_MAX_SIZE 67108864
 
 #define BUS_FDS_MAX 1024
@@ -385,8 +387,7 @@ void bus_close_io_fds(sd_bus *b);
              _slash = streq((prefix), "/") ? NULL : strrchr((prefix), '/'))
 
 /* If we are invoking callbacks of a bus object, ensure unreffing the
- * bus from the callback doesn't destroy the object we are working
- * on */
+ * bus from the callback doesn't destroy the object we are working on */
 #define BUS_DONT_DESTROY(bus) \
         _cleanup_(sd_bus_unrefp) _unused_ sd_bus *_dont_destroy_##bus = sd_bus_ref(bus)
 

src/libsystemd/sd-bus/bus-message.c

@@ -5809,8 +5809,11 @@ int bus_message_remarshal(sd_bus *bus, sd_bus_message **m) {
                 return r;
 
         timeout = (*m)->timeout;
-        if (timeout == 0 && !((*m)->header->flags & BUS_MESSAGE_NO_REPLY_EXPECTED))
-                timeout = BUS_DEFAULT_TIMEOUT;
+        if (timeout == 0 && !((*m)->header->flags & BUS_MESSAGE_NO_REPLY_EXPECTED)) {
+                r = sd_bus_get_method_call_timeout(bus, &timeout);
+                if (r < 0)
+                        return r;
+        }
 
         r = sd_bus_message_seal(n, BUS_MESSAGE_COOKIE(*m), timeout);
         if (r < 0)

src/libsystemd/sd-bus/sd-bus.c

@@ -1609,8 +1609,11 @@ static int bus_seal_message(sd_bus *b, sd_bus_message *m, usec_t timeout) {
                 return 0;
         }
 
-        if (timeout == 0)
-                timeout = BUS_DEFAULT_TIMEOUT;
+        if (timeout == 0) {
+                r = sd_bus_get_method_call_timeout(b, &timeout);
+                if (r < 0)
+                        return r;
+        }
 
         if (!m->sender && b->patch_sender) {
                 r = sd_bus_message_set_sender(m, b->patch_sender);
@@ -4073,3 +4076,36 @@ _public_ int sd_bus_get_n_queued_write(sd_bus *bus, uint64_t *ret) {
         *ret = bus->wqueue_size;
         return 0;
 }
+
+_public_ int sd_bus_set_method_call_timeout(sd_bus *bus, uint64_t usec) {
+        assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
+
+        bus->method_call_timeout = usec;
+        return 0;
+}
+
+_public_ int sd_bus_get_method_call_timeout(sd_bus *bus, uint64_t *ret) {
+        const char *e;
+        usec_t usec;
+
+        assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
+        assert_return(ret, -EINVAL);
+
+        if (bus->method_call_timeout != 0) {
+                *ret = bus->method_call_timeout;
+                return 0;
+        }
+
+        e = secure_getenv("SYSTEMD_BUS_TIMEOUT");
+        if (e && parse_sec(e, &usec) >= 0 && usec != 0) {
+                /* Save the parsed value to avoid multiple parsing. To change the timeout value,
+                 * use sd_bus_set_method_call_timeout() instead of setenv(). */
+                *ret = bus->method_call_timeout = usec;
+                return 0;
+        }
+
+        *ret = bus->method_call_timeout = BUS_DEFAULT_TIMEOUT;
+        return 0;
+}

src/systemd/sd-bus.h

@@ -205,6 +205,9 @@ sd_event *sd_bus_get_event(sd_bus *bus);
 int sd_bus_get_n_queued_read(sd_bus *bus, uint64_t *ret);
 int sd_bus_get_n_queued_write(sd_bus *bus, uint64_t *ret);
 
+int sd_bus_set_method_call_timeout(sd_bus *bus, uint64_t usec);
+int sd_bus_get_method_call_timeout(sd_bus *bus, uint64_t *ret);
+
 int sd_bus_add_filter(sd_bus *bus, sd_bus_slot **slot, sd_bus_message_handler_t callback, void *userdata);
 int sd_bus_add_match(sd_bus *bus, sd_bus_slot **slot, const char *match, sd_bus_message_handler_t callback, void *userdata);
 int sd_bus_add_match_async(sd_bus *bus, sd_bus_slot **slot, const char *match, sd_bus_message_handler_t callback, sd_bus_message_handler_t install_callback, void *userdata);